External fixation apparatus with adjustable pin clamping means

ABSTRACT

An external fixation device for holding bone fragments in place includes a housing having a number of rotationally adjustable pin holders, each of which is held by a clamping member that simultaneously clamps the pin holder within an internal mounting surface of the housing and a bone pin within the pin holder. A first embodiment includes a number of internal mounting surfaces, each of which can include a single pin holder. A second embodiment includes one or two internal mounting surfaces, each of which holds a row of pin holders that is clamped in place by a single clamping member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to apparatus for the external fixation offractured bones, and, more particularly, to such apparatus having meansfor adjustably mounting and clamping a number of bone pins to a housing.

2. Summary of the Background Art

External fixation often provides the best method for holding bonefragments in place during he healing of a severe bone fracture, in whichmultiple bone fragments are formed. In the external fixation process,bone pins or wires ate surgically attached to the individual bonefragments and to intact sections of bone, so that a desired alignment ofmultiple fragments can be maintained during the healing process. Theindividual bone pins or wires are also attached to a frame that isexternal to the body to be held in a fixed configuration. Then, afterthe bone fragments have joined to one another in a satisfactory manner,the bone pins or wires are removed from the bones and from the body inanother surgical procedure. With external fixation, an ability to holdindividual bone fragments in place often makes in possible to achieveresults that cannot be achieved using other conventional techniques,such as casting.

Since serious bone fractures can occur in many different ways in variousparts of the body, forming various configuration of bone fragments, itis highly desirable that a device for external fixation should beconfigured in a variety of different ways, reducing the number ofdifferent types of fixation devices that need to be held in inventory tomeet expected demands. To this end, the patent literature includes anumber of descriptions of fixation devices that can be assembled frommultiple elements in various ways or that can be adjusted to providevarious configurational features.

One method to obtain this kind of flexibility has been to provide aplate having a number of holes defining locations in which bone pins orwires may be clamped, with only a variable subset of the holes beingused in the treatment of a typical fracture. For example, U.S. Pat. No.7,153,303 describes a fixture including several holes for clampingmembers to hold bone pins disposed within an elongated portion and anumber of holes in a rectangular pattern, which can accommodate avariety of pin configurations. Such an arrangement is used, for example,to fasten the elongated portion of the fixture to the shaft of theradius bone within the arm and to attach vatious fragments within abroken wrist to a pattern of pins clamped within the rectangular array.A configuration for applying external fixation to a fractured tibia isalso described as including a frame an elongated lower section forfastening the frame to the shaft of the tibia using bone pins extendingalong a straight line and an arcuate section extending from each side ofthe upper end of the elongated lower section for clamping bone pinsextending into bone fragments within the upper portion of the tibia.U.S. Pat. No. 5,779,703 describes a bone organizer having a number ofholes through which wires are attached to bone fragments.

Another method for obtaining flexibility within an external fixationdevice is to provide a number of clamping elements holding one or morebone pins, with the clamping elements being attached to one another bydevices providing for pivotal adjustment. For example, U.S. Pat. No.5,624,440 describes a fixture including a number of clamping elements,each of which clamps a pair of bone pins extending parallel to oneanother and a rod to which the clamping elements are attached by meansof a pair of pivoting clamps providing for rotational adjustment andclamping about two axes perpendicular to one another. U.S. Pat. No.RE34,985 describes a fixation device having a pair of elongatedcarriers, each of which supports a pair of bone screws that are movablealong the carrier by rotating a spindle. The carriers are joined to oneanother by a connector including a rigid rod and a ball at each end. Theballs are received by partly spherical sockets that can be fixedrelative to the balls through screws. U.S. Pat. No. 4,554,915 describesan external fixation frame including a fixation block from which one ormore arms extend, with a ball and socket joint connecting each arm tothe block for universal movement thereabout. Setscrews are provided fortightening the ball and socket joints. International Pat. Appl. Pub. No.WO 91/111 describes a fixation device having a pair of clamping members,each of which includes a row of holes into which bone pins may beinserted and clamped, with the clamping members being connected by atube, into which a rod extends from one of the clamping members, while aball from the other connecting member extends into a partially sphericalhole within the tube. Setscrews are provided for clamping the rod andball in place within the tube.

What is needed is a bone fixation device having the flexibility ofadjusting the angle at which individual bone pins extend from a housingor frame, preferably with such an adjustment being provided through aclamping device that simultaneously clamps both the linear extension ofthe bone pin, along its length, and its angle relative to the housing orframe.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention, apparatus isprovided for external fixation of bone fragments, with the apparatusincluding a housing, a plurality of pin holders, a plurality of bonepins, and a clamping mechanism. The housing includes at least oneinternal mounting surface and a plurality of apertures. The pin holdersare held within the housing. Each of the pin holders includes a pinmounting hole, a spherically rounded surface engaging at least one ofthe at least one internal mounting surface within the housing and atleast one deformable portion. The bone pins are each held within the pinmounting hole in a pin holder within the plurality of pin holders toextend through an aperture in the plurality of apertures. The clampingmechanism holds each pin holder in the plurality of pin holders in placewithin the housing and deflects the deformable portion of each pinholder to hold the pin in place within the pin holder. The clampingmechanism includes at least one clamping member engaging at least one ofthe pin holders in the plurality of pin holders to hold the pin holderin place within the housing and simultaneously deflecting the deformableportion of the pin holder to hold the bone pin in place within the pinholder.

When the clamping member holding a pin holder in place is loosened, thepin holder can be rotated, with the spherically rounded surface of thepin holder being moved within the internal mounting surface to changethe angle at which the bone pin extends outward from the housing, andthe bone pin within the pin holder can be moved along a pin mountinghole within the pin holder. When the clamping member holding the pinholder in place is tightened, the pin holder is clamped within theinternal mounting surface of the housing, and the pin is clamped withinthe pin holder.

In a first embodiment of the invention, the clamping mechanism includesa plurality of clamping members, each clamping a pin holder in theplurality of pin holders in place within the housing and deflecting thedeformable portion of the pin holder to hold the pin in place within thepin holder. The housing includes a plurality of internal mountingsurfaces. Each clamping member in the plurality of clamping membersincludes a threaded surface and an annular surface engaging thedeformable portion of a pin holder in the plurality of pin holders. Thehousing includes a plurality of threaded surfaces, each disposedadjacent an aperture in the plurality of apertures. The threaded surfaceof each of the clamping members engages one of the threaded surfaces ofthe housing. The housing includes a vertically elongated central portionand a lateral portion extending outward and rearward from each side ofan upper end of vertically elongated central portion: The verticallyelongated central portion includes a first plurality of the internalmounting surfaces, while each lateral portion includes at least one ofthe internal mounting surfaces. As each of the clamping members isrotated in a first direction, an engagement force between thespherically rounded surface of the pin holder clamped in place withinthe housing by the clamping member and the internal mounting surfacewithin the housing is increased to hold the pin holder in place withinthe housing, and deflection of the deformable portion of the pin holderis increased to hold the bone pin in place within the pin holder. Aseach of the clamping members is rotated opposite the first direction,the engagement force between the spherically rounded surface of the pinholder and the internal mounting surface within the housing is decreasedto allow rotation of the spherically rounded surface of the pin holderwithin the internal mounting surface of the housing and to allowmovement of the bone pin within the pin mounting hole of the pin holder.

In a second embodiment of the invention, the housing includes a firstinternal mounting surface, and the clamping mechanism includes a firstclamping member, clamping each of the pin holders within the pluralityof pin holders in place within the first internal mounting surface anddeflecting the deformable portion of each of the pin holders to hold thebone pin therein in place. For example, the first internal mountingsurface is formed as an elongated cylinder having an open end and aclosed end, with the plurality of pin holders disposed in a first rowwithin the elongated cylinder. The first clamping member is movablewithin the open end of the first internal mounting surface to provide aclamping force acting against the pin holder adjacent the open end. Aclamping force is transmitted between the pin holders adjacent oneanother within the first row. Preferably, the device built in accordancewith the second embodiment additionally includes a spacer between eachpair of pin holders adjacent one another in the first row, with theclamping force being transmitted between the pin holders adjacent oneanother through the spacer. The spacer includes a peripheral surfaceengaging the first internal mounting surface of the housing betweenadjacent apertures within the housing and a circular edge engaging theadjacent pin holder at each side of the spacer to hold the pin holder inplace within the housing. Preferably, the first clamping member and theclosed end of the cylinder additionally also include a circular edgeengaging the adjacent pin holder to hold the pin holder 96 in placewithin the housing. The spacer may include a concave surface, with thecircular edge being formed as an outer edge of the concave surface.Alternately, the circular edge may be formed as an edge of a hole withinthe spacer, with the spacer additionally including a flat surfaceextending outward from the circular edge at each side of the spacer.

Each of the pin holders is formed with a spherical external surface,with the pin mounting hole extending in a straight line through thecenter of the spherical surface. For example, each of the pin holdersadditionally includes a pair of slots, perpendicular to the pin mountinghole, extending across the pin mounting hole and partially across thepin holder, forming a deflectable portion of the pin holder and anadjacent end of the pin mounting hole. Alternately, each of the pinholders includes a pair of slots, extending inward along the pinmounting hole, across one another, and perpendicular to one another.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a device for external fixation of bonefragments, built in accordance with a first embodiment of the invention;

FIG. 2 is a fragmentary and partly cross-sectional lateral elevation ofthe device of FIG. 1;

FIG. 3 is a fragmentary front elevation of the device of FIG. 1;

FIG. 4 is a perspective view of a pin holder within the device of FIG.1;

FIG. 5 is a side elevation of a device built in accordance with a firstversion of a second embodiment of the invention and shown attached tobone fragments within a finger;

FIG. 6 is a plan view of the device of FIG. 5;

FIG. 7 is a cross-sectional side view of the device of FIG. 5;

FIG. 8 is an exploded perspective views of adjacent pin holders and aspacer disposed therebetween within the device of FIG. 5

FIG. 9 is a partly sectional end view of a finger having two of thedevices of FIG. 5 attached to bone fragments; and

FIG. 10 is a cross-sectional side view of a device built in accordancewith a second version of the second embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view of a device 10 for the external fixation ofbone fragments, built in accordance with a first embodiment of theinvention. The device 10 includes a housing 12 having a verticallyelongated central portion 14 and a lateral portion 16 extending outward,in the directions of arrows 18, and rearward, in the direction of arrow20, from each side of an upper end 22 of vertically elongated centralportion 14: The vertically elongated central portion 14 includes a firstplurality of the internal mounting surfaces 24; each of which extendsoutwardly from an aperture 25 within the housing 12, while each lateralportion 16 includes at least one of the internal mounting surfaces 24extending from an aperture 25. Some of the internal mounting surfaces 24mount pin holders 26 holding bone pins 28, with the pin holders 26 beingheld in place by clamping members 30 engaging threaded surfaces 32 ofthe housing 12. This arrangement provides for the placement of bone pins28 at various levels extending downward from the upper end 22 of thevertically elongated central portion 14, with the lateral portions 16being inclined relative to one another so that bone pins 28 can extendinward around a fracture area from these portions 16.

In the example of FIG. 1, the device 10 is shown with various bone pins28 attached to a fractured humerus bone 34, holding a number offragments 36 in place at an upper end 38 of the humerus bone 34, withbone pins 28 held within the vertically elongated central portion 14 ofthe housing 12 attached to the shaft portion 40 of the humerus bone 34.Each of the bone pins 28 includes a threaded end 42 that is driven intoengagement with a portion of the bone 34 by a driving tool (not shown)rotating a non-circular surface (not shown) at an end of the bone pin 28opposite the threaded end 42. After the bone pin 28 is fastened intoplace, the bone pin 28 is preferably cut off outwardly adjacent the pinholder 26 in which it is held to limit the distance through which thebone pin 28 extends outwardly from the device 10. The configuration ofthe device 10 is adjustable in several ways, with pin holders 26 beingplaced in a subset of the internal mounting surfaces 24, so that bonepins 28 are placed at locations appropriate for the external fixation ofa particular fractured bone. In addition, the individual pin holders 26are angularly adjustable so that each bone pin 28 can be adjusted andclamped in place through a vertical angle of adjustment 44 and through ahorizontal angle of adjustment 46, with the bone pin 28 additionallybeing adjustable along its axis in the directions of arrows 48.

FIG. 2 is a fragmentary and partly cross-sectional lateral elevation ofthe device 10, particularly showing features of the internal mountingsurfaces 24 within the housing 12, of the pin holders 26, and of theclamping members 30. Each of the pin holders 26 includes a pin mountinghole 50, a spherically rounded surface 52 engaging an internal mountingsurface 24 within the housing, and deformable portions 54 at each end 56of the pin mounting hole 50. Each of he deformable portions 54 is formedby a slot 58 extending inward in a direction perpendicular to the pinmounting hole 50, extending across the pin mounting hole 50 and part ofthe way across the pin holder 26. Each of the of clamping members 30clamps a pin holder 26 in place within the housing 12 and deflects thedeformable portions 54 of the pin holder 26 to hold the pin 28 in placewithin the pin holder 26. Each clamping member 30 includes a threadedsurface 60 and an annular surface 62 engaging a deformable portion 54 ofa pin holder 26. The threaded surface 60 of each of the clamping members30 engages one of the threaded surfaces 32 of the housing 12.

Thus, each of the bone pins 28 extends through an aperture 25 within thehousing 12 at angles, in horizontal and vertical planes relative to thehousing 12, that can be varied by rotation of the spherically roundedsurface 52 of the pin holder 26 through which the bone pin 28 extendswithin the internal mounting surface 24. A bone pin may extend in adirection perpendicular to the aperture 25 or at an angle of inclinationrelative to such a direction of, for example, up to thirty degrees.

FIG. 3 is a fragmentary front elevation of the device 10, showing one ofthe clamping members 30, which is provided with a noncircular surface 64to facilitate rotation of the clamping member 30. As the clamping member30 is tightened by rotation in a first direction, indicated by arrow 66,an engagement force between the spherically rounded surface 52 of thepin holder 26 clamped in place within the housing 12, by the clampingmember 30 and the internal mounting surface 24 within the housing 12 isincreased to hold the pin holder 26 in place within the housing 12 anddeflection of the deformable portions 54 of the pin holder is increasedto hold the bone pin 28 in place within the pin holder 26. As each ofthe clamping members 30 is rotated opposite the first direction of arrow66, the engagement force between the spherically rounded surface 52 ofthe pin holder 26 and the internal mounting surface 24 within thehousing 12 is decreased to allow rotation of the spherically roundedsurface 52 of the pin holder 26 within the internal mounting surface 24of the housing 12 and to allow movement of the bone pin 28 within thepin mounting hole 50 of the pin holder 26. For example, the device 10may be provided with a box wrench (not shown) for loosening andtightening the clamping members 30.

FIG. 4 is a perspective view of one of one of the pin holders 26, whichhas a spherical external surface 68. The clamping member 30 includes apair of slots 58 extending perpendicular to the pin mounting hole 50,inward across the pin mounting hole 50 and partly across the pin holder26, so that a deformable portion 54 is formed between each end 56 of thepin mounting hole 50 and the slot 58 that is nearer to the end 56.

As shown in FIG. 3, the pin mounting hole 50 extends through a center ofthe spherical external surface 68, being divided by the slots 58 into adeflectable part 72 within each of the deformable portions 54 and acentral part 74 extending between the slots 58. When the clamping member30 is tightened by rotation in the direction of arrow 66 to increase anengagement force holding the pin holder 26 in place, the deformableportions 54 are deflected inward, bring the deflectable parts 72 of thepin mounting hole 50 out of alignment with the central part 74 thereof,so that the bone pin 28 is clamped in place within the pin mountinghole. Then, when the clamping member is loosened by rotation oppositethe opposite the direction of arrow 66 to decrease the engagement forceholding the pin holder 20 in place, the deformable portions 54 returnoutward, so that the deflectable parts 72 of the pin mounting hole 50return into alignment with the central part 74 thereof, allowingmovement of the bone pin 28 within the pin mounting hole 50. Forexample, the bone pin 28 may be rotated as much as thirty degrees from acentral position in which the bone pin 28 extends perpendicularly fromthe housing 12.

FIG. 5 is a side elevation of a device 80 for external fixation of bonefragments, built in accordance with a second embodiment of the inventionand shown with pins 82 attached to several fragments of bones 84 withina finger 86. The device 80 includes a housing 88, having a plurality ofapertures 90 through which the pins 82 extend, and a first clampingmember 92, which is turned to clamp the pins 82 in place within thehousing 88.

Features of the device 80 will now be discussed with reference beingmade to FIGS. 6 and 7. FIG. 6 is a plan view of the device 80, whileFIG. 7 is a cross-sectional side elevation thereof. The housing 88includes a single internal mounting surface 94, with the single clampingmember 92, clamping each of a plurality of pin holders 96 in placewithin the first internal mounting surface 94 and deflecting adeformable portion 98 of each of the pin holders 96 to hold the bone pin82 therein in place. For example, the first internal mounting surface 94is formed as an elongated cylinder having an open end 100 and a closedend 102, with the plurality of pin holders 96 disposed in a first row104 within the first internal mounting surface 94. The first clampingmember 92 is movable within the open end 100 of the elongated cylinderto provide a clamping force acting against the pin holder adjacent theopen end 100 of the internal mounting surface 94. For example, the firstclamping member is moved in the direction of arrow 106 by turning anon-circular portion 108 of the clamping member with a threaded portion110 thereof in engagement with a threaded portion 112 of the housing 88.A clamping force, arising from the engagement between the clampingmember 92 and the pin holder 96 adjacent the open end 100, istransmitted between the pin holders 96 adjacent one another within thefirst row 104. For example, the device 80 may be provided with a sockethead wrench for loosening and tightening the clamping member 92.

FIG. 8 is an exploded perspective view of two pin holders 96 and aspacer 114 disposed between the pin holders 96. Preferably, the device80 additionally includes a spacer 114 between each pair of pin holders96 adjacent one another in the first row 104, with the clamping forcebeing transmitted between the pin holders 96 adjacent one anotherthrough the spacer 114. The spacer 114 includes a peripheral surface 116engaging the first internal mounting surface 94 of the housing 88between adjacent apertures 90 within the housing 88 and a circular edge118 engaging the adjacent pin holder 96 at each side 120 of the spacer114 to hold the pin holder 96 in place within the housing 88. Withoutthe spacers 114, the pin holders 96 would be allowed to move into theadjacent apertures 90, so that the pin holders 96 would not be rigidlymounted within the first mounting surface 94. Preferably, as shown inFIG. 7, the first clamping member 92 and the closed end 102 of the firstinternal mounting surface 94 additionally also include a circular edge121 engaging the adjacent pin holder 96 to hold the pin holder 96 inplace within the housing 88.

Each of the pin holders 96 additionally includes a slot 122 extendinginward from each end 124 of a pin mounting hole 126 to form a part ofthe deformable portion 98 of the pin holder 96 at each end 124 of thepin mounting hole 128. The slots 122 at each end 124 of the pin mountinghole 128 extend along the pin mounting hole 126, being disposedperpendicular to one another. Preferably, the slots 122 are formed toextend inward, across one another in a central portion 130 of the pinholder 96, so that the central portion 130 can be deflected by contactwith a concave surface 132 of the spacer 114, even if one of the slots122 is positioned to extend between the concave surfaces 132 of spacers114 at either side of the pin holder 96.

Thus, each of the bone pins 82 extends through an aperture 90 within thehousing 88 at angles, in directions perpendicular to one another, thatcan be varied by rotation of the spherically rounded pin holder 96through which the bone pin 28 extends within the internal mountingsurface 94. A bone pin may extend in a direction perpendicular to theaperture 90 or at an angle of inclination relative to such a directionof, for example, up to thirty degrees.

FIG. 9 is a partly sectional end view of a finger 136 with two of thedevices 80 holding bone pins 82 in engagement with bone fragments 138.Two or more of the devices 80 may be used in this way so that the bonepins 82 can be directed from various locations extending around the bonefragments.

While the pin holders 96, 134 have been described in terms of use withthe device 90 of FIGS. 5-7, it is understood that such pin holders 96,134 can alternately be used with a device otherwise as described abovein reference to FIGS. 1-3, with deformable portions 98, 150 beingdeflected in response to tightening the clamping member 30 to hold pinsin place within the pin holders 56, 134.

FIG. 10 is a cross-sectional side elevation of a device 160 built inaccordance with a second version of the second embodiment of theinvention to include a housing 162 having both a first internal mountingsurface 164 holding a plurality of pin holders 52 in a first row 166 anda second internal mounting surface 168 holding a plurality of pinholders 52 in a second row 170. The device 160 additionally includes afirst clamping device 172, which is turned to clamp and release all ofthe pin holders 52 in the first row 166, and a second clamping device174, which is used to clamp and release all of the pin holders 52 in thesecond row 170. Other features of the device 100 are as described abovein reference to FIGS. 5-9 for the device 80 built in accordance with thefirst version of the second embodiment of the invention. While theexample of FIG. 10 shows three pin holders 52 held within each of theinternal mounting surfaces 168, it is understood that each of theinternal mounting surfaces in general can be configured to hold two ormore pin holders 52.

While a small example of the device 80 has been shown in FIG. 5, beingapplied for the fixation of bones within a finger, it is understood thatthe device 80 and the device 160 of FIG. 2 may be built in any size,having any number of pin holders 96, for the fixation of bone fragmentsin any long bones, including the tibia and the humerus. While theinvention has been described in terms of preferred embodiments andversions thereof with some degree of specific, it is understood thatthis description has been given only by way of example, and that manychanges can be made without departing from the spirit and scope of theinvention, as described in the appended claims.

1. Apparatus for external fixation of bone fragments, wherein theapparatus comprises: a housing including at least one internal mountingsurface and a plurality of apertures; a plurality of pin holders heldwithin the housing, wherein each of the pin holders includes a pinmounting hole, a spherically rounded surface engaging at least one ofthe at least one internal mounting surfaces within the housing, and atleast one deformable portion; a plurality of bone pins, each held withinthe pin mounting hole in a pin holder within the plurality of pinholders to extend through an aperture in the plurality of apertures,wherein an angle, relative to the housing, at which each of the bonepins extends through the aperture is varied by pivoting the pin holderwithin the housing; and clamping means holding each pin holder in theplurality of pin holders in place within the housing and deflecting thedeformable portion of each pin holder to hold the bone pin in placewithin the pin holder, wherein the clamping means includes at least oneclamping member engaging at least one of the pin holders in theplurality of pin holders to hold the pin holder in place within thehousing and simultaneously deflecting the deformable portion of the pinholder to hold the bone pin in place within the pin holder, wherein eachof the pin holders is formed with a spherical external surface, whereinthe pin mounting hole extends in a straight line through a center of thespherical external surface, wherein each of the pin holders includes afirst slot extending in a direction perpendicular to the pin mountinghole across the pin mounting hole and partially across the pin holder,displaced inward from a first end of the pin mounting hole, forming afirst deflectable portion of the pin holder between the first slot andthe first end of the pin mounting hole wherein each of the pin holdersadditionally includes a second slot extending in a directionperpendicular to the pin mounting hole across the pin mounting hole andpartially across the pin holder, displaced inward from a second end ofthe pin mounting hole, forming a second deflectable portion of the pinholder between the second slot and the second end of the pin mountinghole, wherein, when the clamping member is driven into engagement witheach pin holder, a first deformable portion of the pin holder, extendingbetween the first end of the pin mounting hole and the first slot, and asecond deformable portion of the pin holder, extending between thesecond end of the pin mounting hole and the second slot, are deformed sothat a first portion of the pin mounting hole, within the firstdeformable portion of the pin holder, and a second portion of the pinmounting hole, within the second deformable portion of the pin holder,are deflected into misalignment with a central portion of the pinmounting hole, extending between the first and second slots.
 2. Theapparatus of claim 1, wherein the clamping means includes a plurality ofclamping members, each clamping a pin holder in the plurality of pinholders in place within the housing and deflecting the deformableportion of the pin holder to hold the pin in place within the pinholder, the housing includes a plurality of internal mounting surfaces,and the spherically rounded surface of each pin holder within theplurality of pin holders engages an internal mounting surface within theplurality of internal mounting surfaces.
 3. The apparatus of claim 2wherein each clamping member in the plurality of clamping membersincludes a threaded surface and an annular surface engaging thedeformable portion of a pin holder in the plurality of pin holders, thehousing includes a plurality of threaded surfaces, each disposedadjacent an aperture in the plurality of apertures, the threaded surfaceof each of the clamping members engages one of the threaded surfaces ofthe housing, as each of the clamping members is rotated in a firstdirection, an engagement force between the spherically rounded surfaceof the pin holder clamped in place within the housing by the clampingmember and the internal mounting surface within the housing is increasedto hold the pin holder in place within the housing, and deflection ofthe deformable portion of the pin holder is increased to hold the bonepin in place within the pin holder, and as each of the clamping membersis rotated opposite the first direction, the engagement force betweenthe spherically rounded surface of the pin holder and the internalmounting surface within the housing is decreased to allow rotation ofthe spherically rounded surface of the pin holder within the internalmounting surface of the housing and to allow movement of the bone pinwithin the pin mounting hole of the pin holder.
 4. The apparatus ofclaim 2, wherein the housing comprises: a vertically elongated centralportion including a first plurality of the internal mounting surfaces; alateral portion extending outward and rearward from each side of anupper end of vertically elongated central portion, wherein each lateralportion includes at least one of the internal mounting surfaces. 5.Apparatus for external bone fixation, wherein the apparatus comprises: ahousing including a plurality of apertures and an internal mountingsurface and a threaded surface adjacent each of the apertures, aplurality of pin holders, wherein each of the pin holders includes aspherical external surface held within the internal mounting surfaceadjacent an aperture in the plurality of apertures, a pin mounting holeextending in a straight line through a center of the spherical externalsurface, and a pair of slots extending across the pin mounting hole andpartially across the pin holder, wherein each of the slots is displacedinward from one of the ends of the pin mounting hole to form adeflectable portion of the pin holder, extending between the slot andthe end of the pin mounting hole, with a deflectable part of the pinmounting hole extending through each deflectable portion of the pinholder, and with a central part of the pin mounting hole extendingthrough a central portion of the pin holder; a plurality of bone pins,each held within the pin mounting hole of a pin holder within theplurality of pin holders to extend through an aperture in the pluralityof apertures; a plurality of clamping members, wherein each of theclamping members includes a threaded portion engaging a threaded surfaceadjacent one of the apertures within the housing and a surface engagingthe deflectable portion of a pin holder within the plurality of pinholders, wherein, as each of the clamping members is rotated in a firstdirection, an engagement force between the spherically rounded externalsurface of the pin holder and the internal mounting surface in which thepin holder is held is increased to hold the pin holder in place withinthe internal mounting surface, while misalignment between thedeflectable parts and the central part of the pin mounting hole isincreased to hold a bone pin in place within the pin mounting hole, andwherein as each of the clamping members is rotated opposite the firstdirection, the engagement force between the spherically rounded externalsurface of the pin holder and the internal mounting surface in which thepin holder is held is decreased to allow movement the pin holder withinthe internal mounting surface, while misalignment between thedeflectable parts and the central part of the pin mounting hole isdecreased to release the bone pin to move within the pin mounting hole.6. The apparatus of claim 5, wherein the housing comprises: a verticallyelongated central portion including a first plurality of the internalmounting surfaces; a lateral portion extending outward and rearward fromeach side of an upper end of vertically elongated central portion,wherein each lateral portion includes at least one of the internalmounting surfaces.
 7. The apparatus of claim 5, wherein the pair ofslots extend in directions perpendicular to the pin mounting hole. 8.Apparatus for external bone fixation, wherein the apparatus comprises: ahousing including an aperture, an internal mounting surface adjacent theaperture, and a threaded surface adjacent the aperture, a pin holderincluding a spherical external surface held within the internal mountingsurface adjacent the aperture, a pin mounting hole extending in astraight line through a center of the spherical external surface, and apair of slots extending across the pin mounting hole and partiallyacross the pin holder, wherein each of the slots is displaced inwardfrom one of the ends of the pin mounting hole to form a deflectableportion of the pin holder, extending between the slot and the pinmounting hole, with a deflectable part of the pin mounting holeextending through each deflectable portion of the pin holder, and with acentral part of the pin mounting hole extending through a centralportion of the pin holder; a bone pin, held within the pin mounting holeof the pin holder to extend through the aperture; a clamping member,including a threaded portion engaging the threaded surface of thehousing and a surface engaging the deflectable portion of the pinholder, wherein, as the clamping member is rotated in a first direction,an engagement force between the spherically rounded external surface ofthe pin holder and the internal mounting surface is increased to holdthe pin holder in place within the internal mounting surface, whilemisalignment between the deflectable parts and the central part of thepin mounting hole is increased to hold a bone pin in place within thepin mounting hole, and wherein as the clamping member is rotatedopposite the first direction, the engagement force between thespherically rounded external surface of the pin holder and the internalmounting surface is decreased to allow movement the pin holder withinthe internal mounting surface, while misalignment between thedeflectable parts and the central part of the pin mounting hole isdecreased to release the bone pin to move within the pin mounting hole.9. The apparatus of claim 8, wherein the pair of slots extend indirections perpendicular to the pin mounting hole.